The present invention relates to an ultrasonic method and apparatus for automatically controlling the opening and closing of moving doors, particularly sliding doors.
Automatic door control systems are gaining wide-spread use in order to control traffic into or out of enclosed spaces which are heated or cooled by airconditioning systems. Such door control systems not only must detect and respond to objects moving towards the closed doors, but must also provide protection against injury by a closing or opening door, and further, should minimize the time the door is in the open condition in order to minimize wastage of the energy used for airconditioning the enclosed space.
My above-cited patent application describes a method and apparatus for automatically controlling the opening and closing of a door movable over a floor, and a drive for driving the door to its open and closed positions, by: (a) ultrasonically monitoring a predetermined approach area located in front of the door for the entry of an object into the approach area and the movement of the object towards the closed door; (b) ultrasonically monitoring a predetermined opening-door protect area laterally outwardly of the outer end of the closed door, and a predetermined closing-door protect area inwards of the inner end of the door for the presence of an object in the opening-door and closing-door protect areas; and (c) controlling the drive in response to the monitoring operations.
According to the preferred embodiment described therein, a predetermined approach area located in front of the door is ultrasonically monitored by: (i) dividing the predetermined approach area into a plurality of strips; (ii) dividing each strip into a plurality of cells, to thereby define a matrix of cells; (iii) detecting the presence of an object in any of the matrix of cells; (iv) detecting the center of gravity of all the cells in which an object is detected; (v) monitoring the movement of the detected center of gravity with respect to the door; and (vi) controlling the drive to open the door when the detected center of gravity is determined to be moving towards, and at a predetermined speed towards or within a predetermined distance from, the closed door.
As further described in the above-cited patent application, such a method may be implemented by an expansible modular construction by providing an ultrasonic head for each strip of the approach area and by processing the output of each head in a separate channel. Also, the novel method avoids the need to discriminate between different sensors (e.g., by frequency or time discrimination), and also the need to distinguish between many objects in the approach area. Such a method also distinguishes cross-traffic (traffic moving substantially parallel to the doors) which should not open the doors, from approaching traffic which should open the doors.
The present application relates primarily to controlling the closing of the door in order to produce a relatively fast closing, with a reduced danger of causing injury to a person having a body part in the path of the closing door.
At the present time, closing of doors is generally controlled by optical systems, such as those used with respect to elevator doors. However, optical systems generally require wiring within the door, which is expensive to install and to maintain. Further, the detection is effective with respect to limited confined areas through which the optical beam or beams are transmitted, and therefore may not detect an object which may be above, below, or to one side, of the optical beam. Further, such systems may sometimes be "blinded" by sun light.